How to Service a 2-stroke Outboard?

After a long winter indoors many 2-stroke outboards are reluctant to start. A simple service should make yours more reliable.

1. Drain the old fuel

The most common complaint is from people saying it worked fine last year but now it won’t start. This is because petrol evaporates over time, leaving behind an oily, paraffin-type residue which gums up the carburetor. So the first step is to drain the old fuel. Remove the fuel pipe from the carburetor by loosening the clip with a pair of long-nosed pliers. Turn on the fuel tap and drain it into a container. If necessary, remove the tank and clean out any residue or gunge. There is often a small filter just above the fuel tap.

2. Check the spark plug

Remove the spark plug with a socket. The electrode of a healthy plug should be a brown or grey color. If not, clean out any carbon deposits and check the sparking gap matches the recommendation of the engine manufacturer. If the ceramic insulator is damaged or the electrode burnt away, you’ll need a new plug.

3. Check the recoil starter

The recoil starter is held on with three bolts. Remove these and turn the starter over. Check for fraying in the cord and give the spring and bearings a squirt of lubricant.

4. Remove, strip and clean the carburetor

Located on the front of the engine, the carburetor is responsible for ensuring the correct blend of 2-stroke fuel mix with air. A clogged-up carburetor means the engine will run rough and won’t idle properly. The solution is to remove, strip down and clean the carburetor. Undo the clamp and ease the carburetor off its mounting. Make sure you don’t lose the O-ring seal. Remove the screws holding on the bowl. Do this over a tray so you don’t lose any pieces! Sit the bowl in a container of carburetor cleaner, clean any corrosion or residue with a small wire brush, then leave it to soak for a few hours. Next, remove the float. The float height is important, so at this point it’s a good idea to take a photograph of the valve so you can put it back together exactly as you found it. Push out the needle valve hinge pin and remove the float arm. On some engines the needle valve will be linked to the float – so you may have to remove the pin before the float. Next, remove the main jet. Unscrew it, check the hole is clear (inset), and soak it in carburetor cleaner to make sure.

So, prevention is better than cure! Salty water is an engine’s worst enemy – so the engine should be flushed through with fresh water after every use, or it will start to corrode from the inside out.